The present invention relates generally to the field of camera systems, and more particularly, is directed to a method for frame synchronization in a multi-camera system.
In recent years, multi-camera systems have found many applications that require tracking of moving objects and reconstruction of object shapes. For example, a multi-camera system can be used to track customers in a department store so that the time each customer spends in each department can be recorded and analyzed. Such a system can also be used to track the position and head orientation of a computer user sitting at a keyboard, an essential task in building a xe2x80x9csmartxe2x80x9d computer that interacts with the user.
Video telephone and video conferencing equipment can also use a multi-camera system to track the motion of participants and aim the video cameras at a specific participant, such as the person talking. Other applications include surveillance and remote sensing. While it is possible to accomplish some of these tasks with a single camera, multi-camera systems offer a number of advantages. These advantages include the following:
1. Multiple cameras allow more precise information to be obtained from different areas, thus enhancing robust estimation and the final verification process;
2. Multiple cameras can more readily find the actual size and location of an object, thereby eliminating or greatly reducing the intrinsic scale ambiguity problem on shape and location estimates when a single camera is used; and
3. Multiple cameras can combine partial shapes seen from individual cameras through a registration process to form a more complete 3 dimensional (3D) view of the object.
While multi-camera systems have preferred advantages over single camera systems, use of such multi-camera systems present their own challenges. One such challenge is to ensure synchronization among frames captured by different cameras. Although it is possible for a central control unit to distribute a common clock signal to all cameras, such a solution is often very costly to implement.
Accordingly, it is an object of the present invention to obviate the above-noted shortcomings and disadvantages of single and multi-camera systems known in the prior art.
Another object of the present invention is to provide a method of synchronization of the captured frames of a multi-camera system which can be easily and inexpensively performed.
It is another object of the present invention to provide a method of synchronization of the captured frames of a multi-camera system which does not rely on the use of a common clock signal for each of the cameras.
It is another object of the present invention to provide a method of frame synchronization which is fully effective and reliable.
In accordance with the present invention, a technique is provided for calculating the time offsets between different cameras and re-synchronizing the captured frames in a post-processing manner, thus eliminating the necessity of an explicit common clock. This approach allows effective synchronization of frames from different cameras so that a multi-camera system can be used to more accurately analyze the subject under observation.